Processing of grain has been one of the fastest growing agricultural markets internationally in the past twenty years. Each day, thousands of tons of grain arrive at processing facilities before being converted to food, industrial and feed products. Optimal decontamination of these grain products is a critical factor in determining final product quality, not only from an economic perspective, but particularly from a human and animal safety perspective.
As used herein, the term “grain” includes within its scope, but is not limited to, barley, wheat, maize, rye, oats, corn and the grains of any other cereal crops from which starch can be extracted.
Industrial Treatment of Grain
Upon arriving at an industrial grain mill, a grain shipment is first graded according to, inter alia, color, size, level of microbial, mycotoxin and chemical contamination, moisture, oil and protein content, after which the grain is weighed and cleaned in a preliminary first stage screening process to remove dust, chaff and foreign materials. The grain subsequently undergoes a second stage water conditioning process, during which the conditioning water is added to the grain to soften the husks. During this stage, the grain kernels absorb water, which elevates the moisture levels and results in an increase in grain size. This grain is then conveyed to conditioning bins where it resides for anything from 30 minutes to a few hours in the case of the maize and corn milling processes, and up to about 48 hours in wheat milling processes, essentially to permit optimal mobilization of the endosperm and to ease germ extraction
In some instances, tempered grain is subjected to a second dampening and may be further processed through a mechanical surface decontaminator such as the DCPeeler MHXL-W from Buhler AG, which removes the outermost layer (pericarp) of the softened grains and with it contaminating superficial bacteria, mycotoxins and toxic heavy metals.
Thereafter the softened husks are removed and the grain is coarsely ground to break the grain germ, also known as the embryo, loose from other components, such as the endosperm and fiber. The ground grain is carried to degerminators, where the germ is separated and retained for further processing, e.g. extraction of oils, while the germ residue may be used in animal feeds. The grain is further treated in a dry milling process through a series of roller mills, sifters and purifiers to produce finished product flour, meal or the like-milled product.
Those who are engaged in the grain treatment and milling industry will appreciate that there is always a level of superficial contamination on grain surfaces, including dormant toxigenic fungal spores. Upon coming into contact with water these dormant spores develop into a vegetative form of the fungus, whose growth may cause the release of harmful mycotoxins, which may comprise Aflatoxins, Deoxynivalenol toxins, Ochratoxins, Vomerotoxins, Fumonisins and Zearelenone.
The introduction of conditioning water during the second stage water cleaning process is a critical step in grain milling since it provides the only substantial opportunity for impacting upon the microbial quality levels of the final milled product. However, in an essentially dry milling process, the volume of conditioning water introduced must be such that the total grain moisture content after treatment does not exceed 20%, and most preferably be closer to 13% or 18% depending on the grain type. This restriction is set to manage the downstream handling and milling of the grain, and to prevent carry-over of moisture into the final starch-based product. Unless stated otherwise, all grain moisture percentages discussed herein are percentages by weight.
The difficulty in practice is that the quantity of conditioning water that is permitted per ton of grain to be processed such as not to exceed the maximum permissible grain moisture content limit, is substantially inadequate to achieve effective grain surface coating and thus optimal microbial, mycotoxin and chemical decontamination of the grain surface. This limited quantity of conditioning water is, however, sufficient to enable the superficial fungal spores to become vegetative, thus resulting in microbial spoilage and an increased potential for mycotoxin generation.
This problem is exacerbated in wheat milling processes where, because of a much smaller grain size in comparison to that of maize or corn for example, hydration of treated wheat grain in the conditioning bins requires substantially longer periods of time, hence providing a significantly increased opportunity for general microbial growth, and in particular toxigenic fungal growth, on the wheat grain surface.
In an effort to address the problem of fungal growth and mycotoxin accumulation on the grain surface, chemicals and in particular molecular chlorine (as generated by an Aquachlor or equivalent device) and stabilized chlorine-based solutions are often added to the conditioning water to assist with surface decontamination. However, molecular and stabilized chlorine-based solutions are noxious and pose a risk that introduction of such solutions into the conditioning water may lead to the creation of hazardous chlorine or derivative residues on the final grain product, which may be detrimental for human or animal consumption.
Alternatively, mechanical peeling of grain surfaces to remove bacterial, superficial chemical residues and heavy metal contaminants after primary conditioning, may not be sufficiently effective in the optimal peeling of the entire surface of all grains in the batch undergoing processing. Such equipment while claiming substantive decontamination efficacy are unlikely to afford adequate assurance in terms of chemical and microbial sanitation security.
Another risk is the potential for carry-over of chemical decontaminants, particularly molecular and stabilized chlorine-based remedies, into the final flour product. This is a substantial problem in the baking industry, wherein residual chlorine may adversely impact upon the viability of commercial yeast additives that are required during the fermentation process for the leavening of bread dough. Where low concentrations of chemicals, in particular molecular and stabilized chlorine-based solutions, are used for treating conditioning water to obviate any unwanted residues on the grain surfaces, these levels are inevitably too low to afford adequate biocidal capacity, and may promote the development of tolerance by the same microbes to the chemical agents in use.
Baking Industry
In wheat grains, readily available fermentable sugar molecules, e.g. glucose, fructose, maltose and sucrose, serve as metabolic building blocks that are necessary to optimize anaerobic fermentation by commercial yeast strains to generate carbon dioxide, which in turn is essential for the final size, shape and consistency of the baked product. These fermentable sugars are produced by enzymes, amongst others alpha-amylases, which are naturally present in the grain and which serve to assist in the cleaving of discrete sugar molecules from the raw starch aggregate. It is the quantity of these readily available, fermentable sugars which are critical to the pace and magnitude of the anaerobic fermentation as a precursor to the baking process.
However, wild strain and in-process microbial contaminants compete with the commercial yeasts for these fermentable sugars, and serve to compromise optimal and controlled fermentation in the dough mixture, thus resulting in a final baked product with high levels of spoilage microbes and consequently a reduced shelf-life.
In one effort to overcome this uncontrolled contamination, bromate-based oxidants (e.g. potassium bromate) and other oxidants, including ascorbic acid, azodicarbonamide, benzoyl peroxide, chlorine and calcium iodate, are added during the baking process to facilitate water decontamination, flour bleaching, starch mobilization and maturation. However, many of these chemicals may be carcinogenic and as such do not pose a suitable or wholesome solution. In addition, benzoyl peroxide only bleaches carotenoids normally present in flour, but does not have any significant effect on microbial contamination or the color of bran particles.
ECA Solutions
It is well known that production of electrochemically activated (ECA) solutions from diluted dissociative salt solutions involves passing an electrical current through an electrolyte solution in order to produce separable catholyte and anolyte solutions. Those who are engaged in the industry will appreciate that catholyte, which is the solution exiting the cathodic chamber, is an anti-oxidant and normally has a pH of between 8 and 13, and an oxidation-reduction (redox) potential (ORP) of between −200 mV and −1100 mV. The anolyte, which is the solution exiting the anodic chamber, is an oxidant and is generally an acidic solution with a pH of between 2 and 8, and an ORP of between +300 mV and +1200 mV.
During electrochemical activation of aqueous electrolyte solutions, various oxidative and reductive species are present in solution, for example HOCl (hypochlorous acid); ClO2 (chlorine dioxide); ClO2− (chlorite); ClO3− (chlorate); ClO4− (perchlorate); OCl− (hypochlorite); Cl2 (chloride); O2 (oxygen); OH− (hydroxyl); and H2 (hydrogen). The presence or absence of any particular reactive species in solution is predominantly influenced by the derivative salt and the pH of the final solution. So, for example, at pH 3 or below, HOCl converts to Cl2, which substantially increases toxicity levels. At pH below 5, low chloride concentrations produce HOCl, but high chloride concentrations will produce Cl2 gas. At pH above 7.5 hypochlorite ions (OCl−) are the dominant species. At pH>9 the oxidants (chlorites, hypochlorites) convert to non-oxidants (chloride, chlorates, perchlorates) and active chlorine (i.e. defined as Cl2, HOCl and ClO−) is lost due to the conversion to chlorate (ClO3−). At a pH of 4.5-7.5, the predominant species are HOCl (hypochlorous acid), O3 (ozone), O22− (peroxide ions) and O2− (superoxide ions).
For this reason, anolyte predominantly comprises species such as ClO; ClO−; HOCl; OH−;  HO2; H2O2; O3; S2O82− and Cl2O62−, while catholyte predominantly comprises species such as NaOH; KOH; Ca(OH)2; Mg (OH)2; HO−; H3O2−; HO2−; H2O2−; O2−; OH− and O22. The order of oxidizing power of these species is: HOCl (strongest)>Cl2>OCl− (least powerful). For this reason anolyte has a much higher antimicrobial and disinfectant efficacy in comparison to that of catholyte.
RU 2,181,544 suggests a process for improving the quality of baked goods by introducing an electrochemically treated sodium hydrocarbonate solution of pH 9.0-10.0 and an ORP of between −680 mV and −813 mV. In this pH range and using sodium hydrocarbonate, a catholyte solution is produced, which has a low decontamination and sterilization efficacy. Moreover, in theory, HighTest Hypochlorite (HTH) and hypochlorous acid are off-gassed at the alkaline pH. Russian chemical texts suggest the gassing product is chlorine gas which is a product of decomposition of hypochlorite or hypochlorous acid (some believe it is chlorine monoxide-anhydride). Either one is toxic, even in low concentrations, due to irritation to mucous membranes and the respiratory system. The amount of gas released is proportional to the concentration of active chlorine in solution, the state of aggregation, temperature and pH.
RU 2,195,125 proposes increasing the efficiency of grain decontamination in the food industry by (i) washing the grains in an electrochemically activated aqueous catholyte solution of pH 11.0-11.5 and an ORP of −820 mV-−870 mV for 10-12 hours; and (ii) then conducting grain steeping in an electrochemically activated aqueous anolyte solution of pH 2.0-2.5 and an ORP of 1000 mV-11400 mV for 1-1.5 hours. The grain is subsequently germinated at room temperature for 8-10 hours up to a germ length of not more than 1.5 mm.
The first disadvantage of this process is that catholyte at a pH of 11.0-11.5, comprises predominantly chlorides, chlorates and perchlorates, and all reactive chlorine is lost. Accordingly, the catholyte treatment step provides very low decontamination and disinfectant efficacy. The second disadvantage is that subsequent introduction of acidic anolyte results in steeping being done at high Cl2 levels, where all HOCl is converted to Cl2, thus significantly increasing toxicity whilst reducing potential antimicrobial efficacy levels. In fact, as little as 350 ppm HOCl yields as much as 50 ppm Cl2, which is considered toxic to the respiratory tract. No mention is made of dose and thus final chlorine concentration, but one can extrapolate that treatment with acidic anolyte substantially increases the risk of high levels of residual chlorine being carried over into the final milled product.
RU 2,203,936 discloses a method for preparing water for use in various stages of brewage grains using electrochemically activated aqueous salt solution that is prepared from a salt solution comprising 10 grams of salt per liter water. It suggests using anolyte with a concentration of active chlorine in an amount of 0.03%-0.06% for processing of seed yeasts. This equates to about 300-600 ppm chlorine. Notwithstanding the adverse impact upon the viability of the yeast organisms, a level of chlorine as low as 50 ppm as mentioned above, is already considered toxic to the respiratory tract and thus the recommended inclusion rate renders this remedy massively noxious to any procedure for the generation of food for human consumption.